A rolling-element bearing can be of a radial bearing assembly type for supporting an outer part with respect to an inner part as it is known from the prior art, for example from EP-A1-2014935.
This reference describes an arrangement in which the outer part and the inner part rotate with respect to each other about a common longitudinal axis, rollers being radially arranged between the outer and inner parts.
Rollers are advantageously arranged in circumferentially adjacent pockets of an annular bearing cage, the cage being housed between the outer and inner parts. The bearing cage maintains the rollers axially and circumferentially equally spaced and thus enables a uniform load distribution as well as a quiet and smooth running of the bearing. Such bearing cage also prevents direct contact between neighboring rolling elements and thus reduces friction and heat generation in the rolling-element bearing.
A bearing seat is formed on the inner part of the bearing assembly and on which rollers roll. Bearing seat includes a load zone that is subject to a radial load that is substantially stationary relative to the bearing seat. In particular, load zones of this type occur on bearing seats of balancing shafts, more precisely shafts having a center of gravity that is not rotationally symmetric relative to the longitudinal axis about which the shaft rotates in a housing. Such inner parts provided with bearing seats can be formed integrally with a rotating shaft, such as a balancing shaft to be used in a motor vehicle, or separately and mounted on a rotating shaft.
Outer part of a radial bearing assembly supporting in rotation a balancing shaft is stationary and fixed in a housing, the inner part being in rotating movement with respect to the outer part. The outer part comprises an inner cylindrical bore forming a rolling surface for rollers.
Generally, two radial bearing assemblies are provided on a balancing shaft. Both assemblies are axially slid around the balancing shaft from one free end of the shaft, positioned and then fixed in two axial locations of shaft. To ease the assembly of the radial bearing assemblies, the respective inner cylindrical bores of the two outer parts have different inner diameters. The inner diameter of the inner cylindrical bore of an outer part of a first radial bearing assembly close to the shaft free end is strictly greater than the inner diameter of the inner cylindrical bore of an outer part of a second radial bearing assembly that is axially offset with respect to the free end. The difference between the diameters is generally about 0.5 to 1 mm. A cage provided with rollers can then be axially passed through the outer part of the first radial bearing assembly of larger diameter and then be installed with the outer part of the second radial bearing assembly of reduced diameter. Another cage provided with rollers is then installed with the outer part of the first radial bearing assembly. However, the two cages need to be of different diameters, the cage dedicated for the second radial bearing assembly being of reduced diameter with respect to the cage dedicated for the first radial bearing assembly.
Consequently, two different types of cages have to be provided to a balancing shaft application that require to double the stock management, manufacturing and increase costs. Moreover, and even if the cage types are advantageously each well identified by marking, there are very similar with only a slight diameter difference, and it is easy to invert them. This is time consuming for an operator to select the good cage and a potential source of mounting errors, and then risks of failure of radial bearing assemblies during the balancing shaft operation.